Phylum: Charophyta   Family: Desmidiaceae

Cosmarium subreinschii W. Schmidle 1894

A small desmid with 3-undulate sides to the semicells, apex truncate with a central dent occasionally giving a slightly undulate appearance. Chloroplast axile with one pyrenoid.
Single cell dimensions: L: 21.8 µm, B: 17.4 µm, Is: 5.7 µm; Th: c.9.5 µm, L/B: 1.26.
A rare species found in mesotrophic, slightly acidic, waters such as moorland pools and loch-margins.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium. Part 1: Text. Part 2: Plates.
Van Westen, M. (2024). Sieralgen in Drenthe.